Device for the band-spread tuning of radio apparatus



NOV l 1949- J. VAN DER HEEM 2,486,692

DEVICE FOR THE BAND-SPREAD TUNING OF RADIO `APPARATUS Filed April 25, 1946 5y www? Patented Nov. 1, 1949 DEVICE FOR THE BAND-SPREAD TUNING OF RADIO APPARATUS Jan van der Heem, The Hague, Netherlands, as-

signor, by mesne assignments, to Hartford 'National Bank and Trust Company, Hartford,

Conn., as trustee Application April 25, 1946, Serial No. 664,724 In the Netherlands July 1, 1941 i Section 1, Public Law 690, August 8, 194.6

, Patent expires July 1, 1961 In the reception of decimeter waves, i. e. waves between 100 and 10 metres, so-called bandspread tuning is generally employed in order to insure the accurate tuning of radio apparatus. With this method the tuning circuit is` formed in such manner that with a complete stroke manipulation of the tuning member, for example a rotatable-electrode condenser, only4 a very small portion of the wave range is traversed so that the stations operating in this portion oi the range are spread out all over the scale of the tuning member and the tuning to any of these stations may be effected with much greater accuracy than is the case under other conditions.

Different methods of obtaining bandspread tuning are known. A very commonly utilized method involves a circuit arrangement having a xed condenser, a variable condenser and a coil connected in parallel. The range to be covered with bandspreading is determined by the fixed condenser in the coil, and bandspread tuning is effected by means of the variable condenser connected in parallel with the xed condenser. Alternatively bandspreading may be effected by means of a system of condensers connected in parallel with the fixed condenser, one of the said condensers being variable. The ranges in which bandspread tuning has to be eiiected are chosen in this case by switching-in another tuning coil.

In the described method the percentage capacity variation obtained by means of the variable bandspread condenser is equal in each bandspread range so that for eachof these ranges the percentage frequency variation is also equal. Since, however, the stations operate at a constant frequency separation, viz. of 9 kilocycles per second for broadcaststations, the scale distances between the stations become, in spite of the equal percentage frequency va'riation in all bandspread ranges, smaller as the bandspread range is located higher in the frequency spectrum. Hereinafter the term "scale distance is to be construed as the number of dial divisions of the tuning indicator between two stations operating in channels located side by side. In other words: the spreading obtained between the stations decreases for stations operating at the higher frequencies so that the accuracy of adjustment also decreases.

The invention providesa device with the aid of which it is possible to have equal scale distances between stations operating in adjacent channels for all of the ranges to be spread. According to the invention, this is achieved by connecting an inductor having a suitable inductance value in 4 Claims. (C1. Z50-40) series with each of the condensers of the system with which the capacity variation is effected. v

The invention will be explained more fully with reference to the accompanying drawing forming a part of the specification and in which:

Fig. l represents the basic embodiment ofthe invention,

Fig. 2 represents a further and more complicated embodiment, and

Fig. 3 shows diagrammatically a practical form of construction of part of the circuit arrangement according to the embodiment of Fig. 2.

In Fig. 1, a tuning condenser I which, together with any of coils 2, 3, 4, which are switched into circuit by means of a switch 5, aiords tuning in a frequency range over which it is desired to tune by bandspreading. According to the invention, a bandspread condenser is connected, in series with a coil 'I, in parallel with the tuning condenser I. Due to the reactance of the coil 1 part of the reactance of the bandspread condenser 6 `is made inoperative, as it were, which is manifested by the fact that the capacity variation obtained with the aid of the system I, 6, 1, is smaller than the variation which would be obtained with the aid of the system I, 6. The iniiuence of the coil 1 is greater as the frequency is increased, so that in this way the capacity variation obtained by means of the bandspread system decreases as the frequency increases. The percentage frequency variation consequently decreases with an increase of the frequency so that with the simple system according to Fig. 1 the absolute frequency variation can be made equal at least in two different bandspread ranges. This system consequently aiords the possibility of obtaining equal scale distances between the stations in two bandspread ranges whilst in an intermediate range the deviation is still tolerable.

By employing the basic idea of the invention it is possible to extendv the system so that more degrees of freedom are obtained. owing to which it becomes possible to make the frequency variation equal in the absolute sense in each bandspread range. Such a system is shown in Fig. 2 in which constituent parts corresponding to those of the circuit-arrangement according to Fig. l are deno'ted by the same reference numerals. In the circuit arrangement according to Fig. 2 the xed tuning condenser I may, if desired, be

dispensed with, which is represented in the draw-` ing by indicating the condenser in dotted lines. The system shown in Fig. 2 comprises condensers 8, I0 and I2 and coils connected in series with each of the said condensers, viz. coils 9, Il and shown in Fig. 3 wherein-ithe--system Fifor-ffthe capacity variation is representedinthe manner shown in Fig. 2. Here, howeverf'an inductorfQ corresponding to the coil 9 is formed by the wire section Ill-I5, an inductor I|";-;cornespondingd;o

the coil Il by the wire section I -I'bandeau'sin--,l

ductor I 3' corresponding to theccil. 1.3 10ythe wire section |5-I6-I8, the connecting I-points I5 and I6 being adjustable so that both by displacing these points and by giving the connecting wires a determinedgshape it is possible to adlzlstrf they circuitry: itinY ,-thefrequired: inductance values.

What-I: cla-im is:

. circuit arrangement :.forxband-spnead; tuning overatxpluralityi ifoff frequency: bands, c ccmprisingsacpluralityx of-ffprincipal inductances elements, a circuit combinationcomprisingnarparallelncircuitrand sa; A-series circuit =conneicted sin series with each other, saidrparallelf-circuit compricing fz'a :in-rst leg shaving v1a.' series `connected variablecfba-nd-spread capacitor andra'rstbandspread .adjusting inductance elementzi'and f a; second` degli havingl seriesngconnected` .second i capaciter and sa l second -1 band-spread adjusting finductancee eleinent,.;said fseries circuit comprising a third capacitor and 1a third #band-spread adjusting :iinductance oralement, .a fzlbandeselecting switch :coupled to said 'circuit r combination to select lone, fof saidrprincipal :inductancerielements to i'. -tuneq-vover `a fdesirednfrequencyiband,Land means 'i to vary :the -inductance- -pf saidbandspread adjusting iinductancefclements :to-- ladjust the`l range; .ci wtuningr aiorded :byfzsaid "variable capacitor.

11.2.#Arcircuitiarrangement forfbandespread tun-l ingf oyerarazpluraiity of," frequencyzbandsncomprisingsan sinductivef'fbranch.. having yarplurality off principali findnctance f: elements, a capacitive branchecomprisin'g'fza"` variable;- capacitor, and-1': an inductarrc'e-:zconnected inA series #circuit "arrangementxandza fsecond ,capacitor'connected 2in: shunt withvsaidnseries circuit arrangement,` andsband- 4 selecting switch means coupled to said capacitive branch to selectively connect the same to said principal inductive elements f-of ,said -inductive branch. Y

3. A circuit arrangement for band-spread tun- *ing over a plurality of frequency bands, comrprisingan.inductiy,e branch having a plurality nf V`.principal inductive elements, a capacitive branch comprising a variable capacitor and a f'rstfi-nductance'connected in a rst series cir- --Lcuit arrangement zand a second capacitor and a second inductanceconnected in a second series cirCuitarrangement, said first and said second series',circuitparrangements being connected in .ifpafrallelfrelationship, and band selecting switch means coupled toV said capacitive branch to selectively connect-the same to said principal inductive 'elements of said inductive branch.

.fsAacircuit arrangement for band-spread tuning over a plurality off frequency bands, comprisme .an inductivel branchl yhaving .a plurality ofaprincipal inductive elements,v a `,capacitive branchccomprising .a` variable-capacitor and va rstzzinductance `connected in a first series circuitgarrangement, asecond capacitor and a second ,inductance connected in,y a second series circuit varrangementdand .a,.third `capacitor and a tliirdinductance connected .ina third series circuit ,arrangementsaidrst and second series circuitarrangements, being `connected in parallel circuit arrangement and, said third series circuit arrangementl beingl connected .in .series with said parallel circuit arrangement. and band-selecting switch means coupled Ato,saidcapacitive branch to,.selectve1y connect ,thevlsame to said prinQDal inductiveelements of.said inductive branch.

, JAN NAN-DER HEEM.

' REBERENCESCITED IThe following references are of record in the file lciv patent:

UNITIEDSTA'IES PATENTS Number Name `Diate 2,207,254 Holst etal. July 9, 1940 52,252,100 vSpoor Aug. 12, 1941 '2252;919 :Eckard Aug. 19, 1941 1,2A-02,261 `-ABrand June 18, 194'6 .IO'IHER REFERENCES 1Wireless"World,3July1941;pages 180,' 181; 182. (-Copy. in-:Scientiiic Library.) 

